A typical tire parameter sensing system for a vehicle includes a vehicle-based unit and a plurality of tire-based units. Each vehicle tire has an associated tire-based unit. Each tire-based unit includes at least one parameter sensor (e.g., pressure, temperature, etc.), a controller, and transmission circuitry for transmitting a tire parameter signal indicative of the sensed tire parameter(s). Typically, a tire-based unit transmits the tire parameter signal multiple times. For example, the tire-based unit may transmit each tire parameter signal twice, with a predetermined time delay, e.g., 4 milliseconds, between transmissions. The tire parameter signal is transmitted via wireless communication to the vehicle-based unit. The vehicle-based unit includes a receiver for receiving the transmitted tire parameter signals and a display for providing information to the vehicle operator regarding the sensed tire parameter(s).
Various obstacles may be encountered when transmitting tire parameter signals via wireless communication between a tire-based unit and the vehicle-based unit. One obstacle that may be encountered is signal cancellation of the tire parameter signals. At least a portion of the transmitted signal is lost or cancelled during signal cancellation. Signal cancellation may occur as a result of multiple tire-based units transmitting at the same time or as a result of other signal transmissions in the atmosphere. Rotational effects of the vehicle tires may also contribute to signal cancellation.
Another obstacle to wireless communication between a tire-based unit and the vehicle-based unit is interference from electrical noise sources. Many electronic devices associated with the vehicle produce electrical noise. Furthermore, the atmosphere surrounding the vehicle includes electrical noise. The noise may interfere with the reception of the tire parameter signals at the receiver of the vehicle-based unit. When a signal that is received by the receiver of the vehicle-based unit has a signal-to-noise ratio that is less than a predefined value, the receiver of the vehicle-based unit ignores the signal. Thus, it is desirable for a tire parameter sensing system to include structure for helping to overcome these obstacles to wireless communication between a tire-based unit and the vehicle-based unit.